LP38798_15 Datasheet, PDF (17/27 Pages) Texas Instruments – LP38798 High PSRR, Ultra-Low-Noise, 800-mA Linear Voltage Regulator for RF/Analog Circuits

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8 Application and Implementation
LP38798
SNOSCT6B – MARCH 2013 – REVISED DECEMBER 2014
NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
8.1 Application Information
The LP38798 is a high-performance linear regulator capable of supplying a well-regulated, low-noise voltage into
an 800-mA load. The LP38798 can operate over a wide input voltage range (3 V to 20 V) making it well suited for
many post-regulation applications.
8.2 Typical Application: V_OUT = 5 V
V_IN
5.50V
1
IN
2
IN
12
OUT
11
OUT
V_OUT
5.00V
V_EN
GND
C_IN
1 2F
MLCC
C_CP
10 nF
3
IN(CP)
10
OUT(FB)
4
CP
LP38798
SET ^{9 (5.00V)}
5
EN
FB ^{8 (1.20V)}
6
GND(CP)
DAP
7
GND
+ COUT
10 2F
R1
47.5k
R2
15.0k
GND
8.2.1 Design Requirements
Figure 40. Typical Application, V_OUT = 5 V
DESIGN PARAMETER
Input voltage
Output voltage
Output current
8.2.2 Detailed Design Procedure
EXAMPLE VALUE
5.5 V, ±10%
5. V, ±3.5%
500 mA
8.2.2.1 Input Capacitor Recommendations
The LP38798 is designed and characterized for operation with a ceramic capacitor of 1 µF, or greater, at the
input. Note especially that the input capacitances must be located as near as practical to the IN pins
The minimum recommended input capacitance is 1 µF, ceramic or tantalum. However, if the LP38798 is
operating in conditions where input ripple, fast changes in the input voltage, or large changes in the load current
demand are expected, a minimum input capacitance of 10 µF is strongly recommended
Ceramic capacitor tolerance and variations due temperature and applied voltage must be considered when
selecting a capacitor to assure the minimum input capacitance requirement is met over the intended operating
range.
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